This longitudinal study will continue measuring blood pressure, height, weight, skinfold thickness and body girths of 1,082 children, now once annually. The study sample is a stable population of children selected from more than 98% of 10,500 children being all children in grades 1, 2, and 3 of the Minneapolis Public School System in the spring of 1978. All non-black or white children, all children from the top and bottom 5% of the systolic blood pressure (BP) distribution, and a 1/2 sample of black children and a 1/9 sample of white children from the rest of the BP distribution were followed 2x per year in spring and fall of 1978 to 1980 and 1982 to 1985 for BP and body size measurements. These 1,000+ children have also been visited at home in 1978 when extensive psychological, medical history, dietary history, demographic data, and overnight urine collection for Na+, K+ and creatinine have been gathered. In addition, blood pressure, height, weight, medical history, psychological data and Life Event data have been gathered on the parents together with extensive measurements of fat distribution and further medical and dietary history in 1985. In 1981 no screening was performed but consent was obtained to continue screening through the remaining years of school and beyond. In 1982, 22Na+ red blood cell (rbc) efflux rate was measured in 395 children and 617 parents. This will be repeated in 1985 together with measures of sodium lithium countertransport and sodium potassium cotransport. During the course of the study, baseline data and laboratory and Type A classification data will be used to develop predictive equations for blood pressure levels in the highest percentiles in late adolescence and young adulthood. This will include derivation of an index of "tracking" and the predictive value of this index. These may provide etiological clues to essential hypertension and allow indepth study of other factors among children to be found at highest risk. From such proposed predictive studies it will be possible to develop strategies for primary prevention and more detailed examination of etiological factors of essential hypertension.